Groovy Cookbook

The Apache Groovy programming language has extraordinary scripting capabilities. When you combine it with the Grape dependency management system, it turns out that the sky is the limit. In one of the previous blog posts, I explained how you can start compiling Groovy code to the native binary files, using GraalVM’s native-image compiler. This time I tried to do the same with the Groovy script that uses Grape to provide an external library to the classpath. I thought it won’t be possible, but luckily - I was wrong.

Ignoring some of the unit tests when given conditions are not satisfied is a handy feature of a JUnit framework. I guess you have used many times constructions like Assume.assumeTrue(expr) or Assume.assumeNotNull(expr) in your test code. Today I would like to show you one pretty interesting corner case when the usage of Assume.assumeNotNull(expr) throws NPE in the unit test written in Groovy.

Groovy has many useful functions built-in, and one of them is Iterable.combinations() that takes aggregated collections and finds all combinations of items. However, if we take a look its source code, we will find out that it was implemented using very imperative approach (nested for-loops + some if-statement). In this blog post I will show you how to implement the same function using Groovy and tail-recursion algorithm. Enjoy!

Most of the object-oriented programmers prefer constructing algorithms using imperative style over using recursion. This is pretty obvious in the JVM ecosystem, where imperative iteration is much more efficient than recursive function call chain. However, what if I tell you that in Groovy you can take advantage of clean tail-recursive functions without sacrificing performance? Interested? Let’s deep dive into it.

GraalVM became one of the most popular topics in the JVM ecosystem. It promises the highest possible speed of running JVM-based programs (when compiled to native images), hand in hand with the smaller memory footprint. It sounds interesting enough to give it a try. And today we are going to play around a little bit with running simple Groovy program after compiling to a standalone native image.